i am a noob in sw but have been keeping fw fish since i was in first grade and i am just about to get my first sw fish setup. once i am familiar with sw fish i was thinking about getting a shark. what is the smallest shark available to aquarists. the tank i would be getting is 300 gallons 8ft by 2.5 ft by 2 ft. is this big enough. or should i get a bigger one. if i get a bigger one what should the dimensions be